Not
far from the Agriculture Palace was the windmill display area.
Windpower was an important source of power for 1904 farms along with
horsepower and steam power. Electricity was not yet widely
available in most rural areas.

The
scan and the descriptive paragraph below are from the Official
Photographic Views of the Universal Exposition, St. Louis:

Occupying several acres upon Agricultural hill, with their broad faces
set to catch the slightest breeze, is a collection of windmills. The
manufacturer who harnesses the wind for purposes of power no longer
calls his invention a windmill. He adopts the name of aerometer or some
thing equally well-sounding to indicate the character. In the
collection are all sizes and all heights. Water is pumped, wood is cut,
corn is shelled, feed is chopped, grain is ground. These are some of
the performances for which the wind caught by the whirling fans
furnishes the power. One of these mills not only shells corn and grinds
it but lifts the meal to a loft in the barn. The application of the
power to a buzz saw with sufficient force and speed to cut the winter
supply of wood in two days caught the admiration of tens of thousands
of farmersí boys. The lesson of the windmill section was, as taught in
a variety of ways, that, given the wind, all things which require
stationary power are entirely possible to the farmer. It was a matter
of all day wonderment to witness what one of these well oiled and well
braced mills could do with only so much as a five miles-an-hour wind.
Especially interesting is the pump which operates with a huge bucket to
raise a large volume of water a few inches. This is the irrigation
windmill outfit.

Reference:Official
Photographic Views of the Universal Exposition, St. Louis